Untreated natural gas can contain high concentrations, even majority concentrations of up to 80% by volume of acid gas. The acid gas is composed mainly or entirely of carbon dioxide, but can also include hydrogen sulfide, sulfur dioxide, carbon disulfide, hydrogen cyanide and carbonyl sulfide. Such high amounts of carbon dioxide and lesser amounts of other acid gases are unsuitable and unsafe for natural gas used in residential and industrial applications.
Processes for removing acid gases from natural gas typically include membrane separators in which the natural gas is fed to one side of a membrane separator and the acid gas component is caused to diffuse through the membrane, separating it from the natural gas. These processes have drawbacks when the acid gas is present at high concentrations, due to the large size of the membrane separator required for effective treatment. Also, high concentrations of acid gas such as carbon dioxide can plasticize the polymeric separator membranes and reduce their separation efficiency. Also, these processes cannot achieve high removal effectiveness to achieve product gas quality in many cases.
There is a need or desire for a method and apparatus for removing high concentration acid gases from natural gas, which addresses the foregoing size, quality, and durability issues.